This is a randomized, multicenter parallel dosing phase I/II study evaluating three dose levels of HIVIG given every 4 weeks. Nationwide, 30 children will be randomized to receive HIVIG for 6 months at one of the three dosage levels (200 mg/kg, 400 mg/kg, or 800 mg/kg). Clinical and laboratory evaluations and pharmacokinetic sampling will be performed over 6 months and subjects will then be followed for 3 months after the final HIVIG infusion.